However, extensive searching of shipping company records and tickets from that period has failed to reveal any evidence for this claim. The fact that this folk etymology is only recorded 17 years after the terms earliest known appearance (in the 25th September 1918 issue of Punch) also lends weight to the theory that this etymology is merely apocryphal.
"POSH" is a song, on this very subject, from the musical Chitty Chitty Bang Bang. In the original film, it was performed by Lionel Jeffries.